In a manufacturing method of a semiconductor device of a resin molded type, in order to make it join to an external equipment good, a plating film is formed on a surface of the lead for external connection. A good solderability is obtained when the lead for external connection is connected with a mounting substrate etc. by forming this. As a material of a plating film, a Sn—Pb alloy which added Pb (lead) to Sn (tin) has been used widely. This alloy is excellent in wettability and can improve bond strength (for example, refer to Patent Reference 1).
However, since it is required from consideration of an environment in recent years that lead should not be used for an electronic equipment, the material which does not contain lead is used for the plating film. For this reason, a Sn—Bi alloy which added Bi (bismuth) to Sn has been used instead of Sn—Pb alloy.
When alloy, such as Sn—Bi, is used as a plating film, the metal whisker from a surface of the plating film occurs. When this grows and it becomes long, the trouble that the adjoining leads for external connection connect may be generated. A generation of the whisker can be reduced by performing annealing treatment etc. after formation of a plating film (for example, refer to Patent Reference 2).
[Patent Reference 1] Japanese Unexamined Patent Publication No. 2004-200249
[Patent Reference 2] Japanese Unexamined Patent Publication No. 2002-368175